352 
Review : 
theoretical paragraphs attached to them, carefully stated and 
qualified as they are, deliberately put before the student one view 
only of this highly debateable topic. This is no doubt an expression 
of the “deliberate judgment” referred to in the preface, but it is 
permissible to doubt the soundness of that judgment in this instance, 
considering the present state of knowledge and opinion. 
It is said on p. 121 that “ the central region of the stem and 
seta of Polytrichaceae almost suggest conducting tissue.” On page 
342, in the physiological part of the book, the experimental 
evidence for conduction in the central strands of elongated cells of 
“ the sporophytes of liverworts and mosses” is said to be “ weak.” 
This last statement is to some extent true, but it is difficult to 
understand how anyone acquainted with the structure of the 
Polytrichaceous stem can doubt the conducting functions of the 
comparatively highly differentiated central cylinder. The words 
“ almost suggest ” convey quite a wrong impression of the facts. 
On page 143 it is stated that the partition of the synangium of 
Tmesipteris is sterilized sporogenous tissue, and that this is 
“ proved by its development and by the fact that in exceptional 
cases it functions as sporogenous tissue ; ” also that in Spheno- 
pliyllum the “ sporangiophore development is carried much farther 
than in Psilotum and Tmesipteris, resulting in a multiplication of 
sporangia by means of the sporangiophore.” The evolutionary 
theory here suggested is a possible one, but it is not the only 
possible one, and no part of the evidence for it can be fairly 
described as “ proved ” by any known fact. 
The description and figure (140) of the vascular bundles of 
Equisetum are not at all good. The xylem is said to be “ hardly at 
all developed, its position being occupied by a small air passage 
(p. 146).” Not only the primitive protoxylem strand of the inter¬ 
node, but also the lateral metaxylem strands and the nodal xylem 
are thus quite ignored. 
The word poly stele is used (on p. 157) in the sense apparently 
of polydesmic stele , for it is said to be the condition “ in which 
several concentric bundles traverse the stele without organisation 
into a definite cylinder.” Both the word and the definition are 
open to objection—-the word because it suggests the well-known 
word polystelic which means “ having many steles,” and the 
definition because the emphasis should be laid on the fact that a 
cylinder is still present, but is perforated by gaps. The stele of 
Pteris aquilina is not, like the cauline vascular system of certain 
